The present invention relates generally to the field of circuit cards and, in particular, to circuit cards having a single ground plane with logic devices connected thereto.
Three-ground electrical systems, such as many circuit cards deployed in central offices or remote units of telecommunications systems or the like, are often connected to two-ground electrical systems, such as telecommunications systems. For example, some three-ground circuit cards have a logic-ground plane to which ground pins of logic devices of the circuit card are connected, a separate chassis-ground plane, and a battery-return of a power supply of the circuit card, e.g., a DC-to-DC power supply or converter for providing voltages to the logic devices. Telecommunications systems typically have a chassis-ground, e.g., a housing (or rack) of a central office, remote unit, or the like for containing the circuit cards connected to earth ground, and a battery-return connected to the chassis-ground at a single location.
One method for connecting three-ground circuit cards to two-ground telecommunications systems involves using a circuit card having the logic-ground plane connected to the battery-return of the circuit card and having the logic-ground capacitively coupled to the chassis-ground plane of the circuit card using one or more relatively high-voltage capacitors. The chassis-ground plane is connected to the chassis-ground of the telecommunications system and the battery-return of the circuit card is connected to the battery return of the telecommunications system.
One problem with this method of connection is that many of the logic devices of the circuit card are susceptible to electrostatic discharge (ESD), and the capacitive coupling to the chassis-ground plane and thus earth ground does not provide a clear, low-impedance path for the ESD to go to earth ground. Moreover, logic devices often generate electromagnetic interference (EMI). Again, the capacitive coupling to the chassis-ground plane and thus earth ground does not provide a direct, low-impedance path for the EMI to go to earth ground. Therefore, the EMI can radiate, often affecting the performance of other equipment of the telecommunications system.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternatives to circuit cards having two separate ground planes where one of the ground planes is connected to a battery-return and is capacitively coupled to the other ground plane.
The above-mentioned problems with circuit cards having two separate ground planes where one of the ground planes is connected to a battery-return and is capacitively coupled to the other ground plane and other problems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification.
In one embodiment, an electronic system is provided. The electronic system has a chassis-ground. The electronic system includes one or more circuit cards. Each of the one or more circuit cards includes a single ground plane connected to the chassis-ground and a logic device having a ground pin connected to the single ground plane. The connection between the ground pin and the single ground plane provides a direct path between the logic device and the chassis-ground. The one or more circuit cards are adapted to a connect to a battery, where the battery is connected to the chassis-ground.
In another embodiment, a circuit card is provided. The circuit card includes a single ground plane connectable to a chassis-ground and a logic device having a ground pin connected to the single ground plane. The connection between the ground pin and the single ground plane provides a direct path between the logic device and the chassis-ground. A power supply is connected to an input pin of the logic device for providing a logic voltage to the logic device. The power supply is connectable to a battery.
In another embodiment, a method for grounding a logic device of a circuit card is provided. The method includes connecting a ground pin of the logic device to a single ground plane of the circuit card and connecting the single ground plane of the circuit card to a chassis-ground. Connecting the ground pin of the logic device to the single ground plane of the circuit card and connecting the single ground plane of the circuit card to the chassis-ground provides a direct path between the logic device and the chassis-ground.
In yet another embodiment, a method for manufacturing a circuit card is provided. The method includes disposing a logic device on a substrate and disposing a single ground plane within the substrate. The single ground plane is connectable to a chassis-ground. Connecting a ground pin of the logic device to the single ground plane is also included in the method. Connecting the ground pin of the logic device to the single ground plane provides a direct path between the logic device and the chassis-ground.